Just a quick linker addendum - I wrote a DLL system for MS-DOS a few
years ago, and The MS-DOS Encyclopedia was great. Not ALL issues are
covered though, and a good way to supplement your knowledge is to order
the OMF developers kit from Microsoft (sorry, can't remember the exact
name, that was too many cans of coke ago) which has the latest format
updates documented (and a useless diskette). The manual took a bit
of puzzling out at first, but when I got into it, I could not have
completed the job without it.